Turf tests

Ron Dobbin, the SRP agricultural specialist who planned the test plots, checked the Acclima timer used to irrigate the area.

Turf tests yield unexpected results

SRP’s DesertWise Landscape Research Exhibit

Published January 2007 - Turf West Magazine
By Don Dale

This just in from Phoenix: The turf varieties that are the most popular or best known may not be the best for your facility in the desert-and do you know that artificial turf in not free from water use or maintenance?

This info, along with other turf facts, comes from the Salt River Project’s (SRP) DesertWise Landscape Research Exhibit. SRP is the big water and power utility in the Phoenix area, and it has been conducting turf research for the last two years in order to assess water conservation values of grass in landscaping, as well as demonstrate to the public and landscapers how different turf varieties perform.

Probably the biggest news was the identification of one turf variety that performed well, head and shoulders above others in the trial in some ways and, it was a surprise. The variety was Princess 77, a hybrid bermudagrass from Seeds West that can be grown from seed.

“There are a couple of real good performers,” said Marc Campbell, water resources planning analyst for SRP and leader of the research effort. Princess 77 really stood out for both water stress resistance and green color in the winter. There were five varieties of hybrid Bermudas in the trial and one of seashore paspalum. The test varieties were selected because of their interest level from local municipalities and the public, and because they have been touted as low water use grasses.

The test plots were small, about 10 by 15 feet, at the SRP’s PERA Club, with a western exposure and morning shade from an adjacent building. The test was begun in 2994. The five Bermudas were Bull’s-Eye, Midiron, Tifsport, Celebration and Princess 77. The paspalum was Sealsle 1. The idea was to measure soil moisture content and use visual observations to determine which grass stressed less as irrigations were lowered-by 10, 20, and 30 percent-during the heat of the summer.

Although all the varieties were in good condition at the beginning of the drought simulation, they were severely tested for two weeks as water levels were lowered . After each cycle, the grasses were well watered and rejuvenated before the next drought simulation.

Campbell says that TifSport, Sealsle 1 and Princess 77 all weathered the summer conditions well until they reached about 15 percent soil level, when they began showing some stress. As water levels were lowered further, only the Princess 77 still looked very good. It performed well right into the 30 percent deficit situation.

Furthermore, it was the only variety that stayed green in both summer and winter, and as such it would have been the only turf to not require winter overseeding in a golf course or home owner association seeting. “The Princess 77 had that nice green color,” Campbell says. This was a majorfinding because one objective of the study was to identify grasses that could reduce water consumption in the winter when a lot of overseeding with ryegrasses is done in Arizona. Those ryegrasses use a lot of water and require a lot of effort to overseed.

An informal assessment that Campbell came to after looking at deficit irrigations is that it requires so much water to keep any turf variety green in the summer that it may be more practical to let that turf go brown. That would save enough water to plant rye in the winter, when there is more recreational turf use in Phoenix . Obviously, one attraction of the Princess77 was that, although it would have to be watered in the winter, it would not have to be overseeded.

“That was one reason we chose it as our number one turf,” says Ron Dobbin, the SRP agriculture specialist who was in charge of growing the test turf plots. He points out that this was a “real world” test, not a scientifically valid randomized plot selection, and that all varieties did well under normal and mildly stressful conditions. The test was founded by SRP and received additional support from about 40 industry companies and interested agencies.

Three more plots were devoted to three kinds of synthetic turf in order to determine if they had any water use requirements, to monitor their surface temperatures and to assess overall appearance and maintenance requirements. There is a lot of interest among landscaping circles about artificial turf. These findings were also somewhat surprising.

Campbell says the synthetic turf looked pretty good all the time, but it had some drawbacks. First, it does require some water, because it has to be hosed down after storms or pet deposits. Second, it became extremely hot. Surface temperatures reached an average of 155 degrees and water was required to cool surrounding vegetation. This was hotter than asphalt (148 degrees) and much hotter than natural grass, which averaged 97 degrees.

In addition, synthetic turf required “moderate maintenance,” including sweeping or vacuuming after winds. One surprise was that it requires weed control, especially if proper ground preparation isn’t done. Weeds like nutsedge can come right through the fabric or around the edges. It is also costly to install, at $8 to $12 per square foot, about four times what it costs to install natural turf.

In another part of the SRP PERA area, zoysia, St. Augustine and buffalograss were planted in observational plots. The zoysia and St. Augustine performed fairly well under normal watering conditions, but the testers were disappointed in the buffalograss. The buffalograss plot became contaminated by common bermuda grass, and when watered it could not compete with the bermuda. It had to be replanted, and even then was overtaken by bermuda. That told them that the buffalograss probably wouldn’t be able to grow in this area unless in a virgin area or area that had beed sterilized of bermuda.

“The conservation community here was very interested in that grass,” Campbell says, but the results have discouraged him from recommending it in this area. He plans to replant it and see what happens the next time.

Another trial was on the use of soil amendments to see if they could improve irrigation efficiency, grass health and water retention. These were tested in turfed water retention basins in the parkland setting.

Five soil amendments, both organic and inorganic were tried. They were Organic Gem, a fish hydrosate; Complete Biological Extract (CBX), an organic plant mineral compound; BioFlora, a bioorganic nutritional system; and either Nutrimoist or Enviromoist, polymer crystals injected into the ground to absorb water. They were applied at the labeled recommendations at prescribed intervals.

The results were interesting. Both the CBX and the Organic Gem brands helped “extend the irrigation intervals,” in Campbell’s words. They improved soil percolation and turf health, and salt levels were reduced below those of the control areas.

“You’re using a lot of salt-based nutritional materials out there” in fertilizers, Dobbin notes, and the two organic amendments helped to reduce those spikes. One benefit seemed to be in the micronutrients and microbial activity in those products, which helped create air spaces in the soil and improved water penetration in water retention areas. Fairly constant pH levels were maintained, turf was green and irrigation intervals were extended up to three days beyond the schedule set by a SMART irrigation controller.

The BioFlora application yielded good short-term results, but over the long term this area had more soil compaction and became hydrophobic and anaerobic. There were drainage problems, exemplified by a big rain that filled the CBX and BioFlora areas with water. Within 20 days the CBX area had drained, while the BioFlora area still had water. The two top organic performers also were used on a nearby softball field and helped conserve water use there.

The researchers were a little surprised that the polymer-based amendments did not perform well, but the trial may have been prejudiced by a break in an irrigation line. Even so, those amendments retained salt in the root zone, which stressed the turf.

Some other small observational trials were conducted in the SRP study. One was the use of subsurface drip irrigation lines on a demonstration lawn planted in common bermuda grass using an Aquaconserve ET controller for timing. “It did great,” Dobbin said, but there was a lot of effort put into the maintenance learning curve. Results aren’t out yet, although they know it used less water than sprinklers.

A comparison xeriscape area was also installed in front of one building, with 16,000 square feet being converted from turf. As expected, it performed extraordinarily well in water use, although admittedly a significant percentage of the area was inert objects, such as rocks. Still, it opens the eyes to know that it used .26 acre-feet in the Phoenix area.

SRP spokesman Jeff Lane says that the utility, as the largest supplier of water in the area, feels compelled to look at water conservation methods. It wants to be a responsible steward of a limited water supply, especially in times like these.

“We’re in the eleventh year of drought here in Phoenix,’ Lane says, and despite some brief respites, that drought could go on indefinitely, even as the population explodes. Thus, the rationale behind these tests, which will continue until spring of 2007. As part of the DesertWise Landscape Research Exhibit, the test area is serving as a demonstration and education resource, and Campbell is already giving presentations around the valley on test results.

“There’s a lot of people that still like grass,” Campbell said. So, it behooves all turf installers to use all the information at their disposal to select the best turf varieties and application methods to reduce water use.